Cocoa powder extracts exhibits hypolipidemic potential in cholesterol-fed rats

INTRODUCTION

Hypercholesterolemia and oxidative stress are risk factors of cardiovascular diseases.

OBJECTIVES

This study investigated the hypolipidemic effect of cocoa powder extract (CPE) in an experimental model of hypercholesterolemia, using Questran as a reference.

METHODS

Hypercholesterolemia in rats was induced by oral administration of 30 mg/kg cholesterol for eight weeks. Three groups concurrently received Questran (0.26 g/kgb) and CPE (100 mg/kg and 200 mg/kg) respectively. Hypercholesterolemia and dyslipidemia were assessed by lipid profile. Reduced glutathione (GSH), Superoxide dismutase (SOD), Catalase (CAT), Glutathione-S-transferase (GST) and malondialdehyde (MDA) level were also assessed to evaluate the antioxidant status of rats.

RESULTS

There was 56% and 97% increase in total and LDL-cholesterol and 59% decrease in HDL-cholesterol levels on cholesterol administration. Concurrent administration of CPE (100 mg/kg) significantly (p < 0.05) decreased total cholesterol (19%) and LDL-cholesterol (22%) and increased HDL-cholesterol (286%) levels while at 200 mg/kg, 55% and 64% reductions in total and LDL-cholesterol and 250% increase in HDL-cholesterol levels were observed. No significant changes were observed in phospholipid levels. Body weights of rats were not significantly different among groups and CPE (100 mg/kg) ameliorated the cholesterol-induced enlargement of the liver and heart by 14% and 15% respectively and at 200 mg/kg by 21% in the heart. GSH and CAT were significantly depleted, and MDA and SOD significantly elevated in liver and heart of Cholesterol-fed rats. No significant changes in GST, alanine and aspartate aminotransferases occurred among groups. CPE treatment modulated these changes.

CONCLUSION

Cocoa powder possesses hypolipidemic potential and may be relevant in treating pathologies with dyslipidemia as an underlying cause.

Influence of cholestyramine on the pharmacokinetics of rosiglitazone and its metabolite, desmethylrosiglitazone, after oral and intravenous dosing of rosiglitazone: impact on oral bioavailability, absorption, and metabolic disposition in rats

The possible influence of the bile acid-sequestering agent cholestyramine (CSA), which is a basic co-medication in hypercholesterolemic patients, on the pharmacokinetics of rosiglitazone (RGL) and its circulating metabolite desmethylrosiglitazone (DMRGL) was investigated following a single oral and intravenous dose of RGL to Wistar rats. The pharmacokinetic parameters of RGL and DMRGL were evaluated following oral or intravenous administration of RGL to rats at 10 mg kg-1 with and without pre-treatment (0.5 h before RGL administration) of CSA at 0.057, 0.115, 0.23 and 0.34 g kg-1 doses. With an increase in CSA dose there was dose-dependent decrease in area under the curve (AUC)(0-infinity) and Cmax with no change in Tmax, Kel and t1/2 values for both RGL and DMRGL following oral administration of RGL. The oral bioavailability of RGL was reduced by 19.9, 35.6, 53.8 and 72.0% in rats following pre-treatment with CSA at 0.057, 0.115, 0.230 and 0.340 g kg-1, respectively. There was no change in the above-mentioned pharmacokinetic parameters for RGL and DMRGL in rats when RGL was given intravenously following pre-treatment with the above-mentioned oral doses of CSA. Another objective of the study was to determine the effect of staggered oral CSA dosing at 1, 2 and 4 h after oral RGL administration at 10 mg kg-1. AUC(0-infinity) of RGL and DMRGL was reduced following CSA staggered administration at 1 h, whereas 2- and 4-h staggered dose administration of CSA had no effect on the AUC(0-infinity) of RGL and DMRGL. Irrespective of CSA staggered dose administration there was no change in other pharmacokinetic parameters, namely Cmax, Tmax, Kel and t1/2. The apparent formation rate constant (Kf) of DMRGL was also calculated to show that only the absorption of RGL was affected, not the apparent formation rate of DMRGL. The authors also studied the in vitro adsorption of RGL (100, 250, 500 microg ml-1) at various pH conditions (pH 2, 4 and 7) and different concentrations of CSA (15, 30, 60 and 120 mg ml-1). The percentage binding of CSA was in the range 50-72% (at pH 2), 74-89% (at pH 4) and 97-100% (at pH 7). In conclusion, we carried out a systematic investigation demonstrating mechanistically the interaction potential of RGL when co-administered with CSA. The applicability of the metabolite data after intravenous and oral dosing and pH-based binding experiments further adds credence to the key findings.

Effects of short-term treatment with diclofenac-colestyramine on renal function and urinary prostanoid excretion in patients with type-2 diabetes

OBJECTIVE

To determine the effect of short-term administration of diclofenac-colestyramine on glomerular filtration rate (GFR), renal plasma flow (RPF) and urinary excretion of prostanoids in patients with type-2 diabetes without and with impaired renal function.

METHODS

In the randomised, single-blind, placebo-controlled, two-period crossover study, 32 patients with type-2 diabetes (group 1: 16 patients without impaired renal function, creatinine clearance > or =80 ml/min and group 2: 16 patients with impaired renal function, creatinine clearance 30-79 ml/min) received 140 mg diclofenac-colestyramine (corresponding to 75 mg diclofenac sodium) or placebo twice a day on days 1 and 2 and once on day 3 with a wash-out period of 6 days between the two periods. GFR was assessed using both measurement of creatinine clearance and calculation of inulin clearance and RPF was assessed using calculation of para-aminohippurate (PAH) clearance after the short-term administration on day 3. Urinary excretion of prostanoids (PGE(2), PGE-M, 6-keto-PGF(1alpha), 2,3-dinor-6-keto-PGF(1alpha), TxB(2), 2,3-dinor-TxB(2) and 11-dehydro-TxB(2)) were measured before and after drug intake.

RESULTS

Comparison with placebo showed no effect of diclofenac-colestyramine on creatinine, inulin or PAH clearance ( P>0.05) in patients with type-2 diabetes either without or with impaired renal function. The differences in creatinine, inulin and PAH clearance between the two groups of patients were not influenced by diclofenac-colestyramine. Urinary excretion of PGE(2), PGE-M, 6-keto-PGF(1alpha), 2,3-dinor-6-keto-PGF(1alpha), TxB(2), 2,3-dinor-TxB(2) ( P=1.89) and 11-dehydro-TxB(2) was significantly reduced by diclofenac-colestyramine.

CONCLUSION

These results indicate that proven non-specific cyclooxygenase inhibition by short-term administration of diclofenac-colestyramine did not affect renal haemodynamic function (GFR, RPF) in patients with type-2 diabetes either without or with impaired renal function.

Comparative scintigraphic assessment of the intragastric distribution and residence of cholestyramine, Carbopol 934P and sucralfate

It has been demonstrated that orally administered cholestyramine is distributed throughout the stomach and provides prolonged gastric residence via mucoadhesion. Gamma scintigraphy was used to compare the gastric emptying and residence of this resin with two formulations known to exhibit retentive or bioadhesive properties, Carbopol 934P and sucralfate. Fasted normal subjects received a single radiolabelled dose and gastrointestinal transit was monitored for 6 h. The subjects were fed after 4 h to determine the effects of inducing a fed pattern of motility on the retention of the formulations. Initial gastric emptying was similar (Mean T50+/-S.E.M.: cholestyramine=66.93+/-9.39 min; Carbopol=56.57+/-11.96 min; sucralfate=48.33+/-11.07 min; P=0.548: n=10), however, the emptying of cholestyramine slowed beyond 2 h. This resulted in greater residence for cholestyramine (Mean AUC0-6+/-S.E.M. (relative units)=11516+/-686 versus 7657+/-1170 versus 6170+/-998; cholestyramine versus Carbopol versus sucralfate; P=0.004: n=10), with approximately 25% remaining in the stomach at 6 h compared to 3.84 and 2.65% of Carbopol and sucralfate, respectively. Cholestyramine was also distributed widely throughout the stomach whereas Carbopol and sucralfate were concentrated in the body and antrum. Thus, as cholestyramine had a comparable emptying time to Carbopol and sucralfate but greater gastric residence and wider distribution, it could provide a potential mucoadhesive drug delivery system targeting the gastric mucosa for treatment of conditions such as Helicobacter pylori infection.

Effect of resin surface charge on gastric mucoadhesion and residence of cholestyramine

Previous studies performed on excised gastric tissue and in healthy volunteers revealed that the ion exchange resin, cholestyramine, exhibits mucoadherent behaviour. This study was designed to elucidate whether surface charge affected this behaviour. Gamma scintigraphy was performed on fasted normal subjects following oral administration of cholestyramine or the cationic exchanger Amberlite(R) IRP-69, either uncoated or polymer-coated to mask their charge. Subjects were fed after 4 h. The initial gastric emptying of all formulations was similar (T(50) values (mean+/-S.E.M.): cholestyramine=85.86+/-9.16 min; IRP-69=76.09+/-9.23 min; polymer-coated cholestyramine=72.0+/-12.64 min; polymer-coated IRP-69=70.25+/-10.57 min: P=0.724). However, after 3 h the emptying pattern of cholestyramine was slower than that of IRP-69. This resulted in greater retention times than IRP-69 (AUC(0-6) values (relative units)=15,200+/-1093 versus 9452+/-811; cholestyramine versus IRP-69: P=0.0004). This effect was reduced by polymer-coating the cholestyramine. Serial images showed that cholestyramine was trapped in the oropharyngeal region and subsequently displaced by the meal, resulting in higher levels of activity remaining at 6 h. Thus, cholestyramine exhibited prolonged gastric residence via mucoadhesion and was distributed throughout the stomach. The surface charge of the resin was found to have a contributory role. These materials may have potential for the delivery of drugs in the topical treatment of the gastric mucosa, for example in the eradication of Helicobacter pylori.

Effects of cholestyramine on hepatic cholesterol 7alpha-hydroxylase and serum 7alpha-hydroxycholesterol in the hamster

Cholestyramine increases activities of hepatic cholesterol 7alpha-hydroxylase and serum levels of 7alpha-hydroxycholesterol. To examine if serum 7alpha-hydroxycholesterol levels parallel with enzyme activity, 0, 0.5, 1, 2, 4, and 10% of cholestyramine was administered to female golden Syrian hamsters for 28 d in the dose-dependent study, and 2% cholestyramine for 0, 1, 3, 7, 14, 21, and 28 d in the time-dependent study. In the dose-dependent study, hepatic and serum cholesterol levels were significantly decreased dose-dependently when more than 0.5% of cholestyramine was fed for 28 d. Cholestyramine increased the cholesterol 7alpha-hydroxylase activity in a dose-dependent manner, while the serum 7alpha-hydroxycholesterol level was essentially unchanged. No correlation was found between the serum level and the hepatic enzyme activity. In the time-dependent study, hepatic and serum cholesterol levels markedly decreased when 2% cholestyramine was fed for longer than 3 d. The serum triglyceride level increased significantly for the first 7 d and then decreased. Cholesterol 7alpha-hydroxylase activity increased significantly as early as day 1, reached maximum activity level on day 7, and then kept the significantly high values until day 28. The serum 7alpha-hydroxycholesterol level significantly increased for the first 7 d and decreased to the pretreatment level thereafter. 7Alpha-hydroxycholesterol levels significantly correlated with serum cholesterol and triglyceride levels. We conclude that the serum 7alpha-hydroxycholesterol level does not always reflect the activity of hepatic cholesterol 7alpha-hydroxylase, when cholesterol metabolism is severely disturbed by cholestyramine.

SK&F 97426-A: a novel bile acid sequestrant with higher affinities and slower dissociation rates for bile acids in vitro than cholestyramine

SK&F 97426-A is a novel bile acid sequestrant that is threefold more potent than cholestyramine at increasing bile acid excretion in the hamster. SK&F 97426-A is a quaternary alkylammonium polymethacrylate that was selected for comparison with cholestyramine in vivo because of its superior in vitro bile acid binding properties. Association, dissociation, affinity, and capacity experiments were performed under physiologically relevant conditions with the most abundant bile acids found in human bile. The bile acids came to equilibrium with SK&F 97426-A and cholestyramine within approximately 30 min and 6 min, respectively. SK&F 97426-A and cholestyramine had similar capacities for all the bile acids (between 2.5 and 4 mmol/g) and both had similar, very high affinities and slow dissociation rates for the dihydroxy bile acids. However, SK&F 97426-A had much higher affinities for the trihydroxy bile acids glycocholic acid and taurocholic acid than did cholestyramine. Dissociation of glycocholic acid and taurocholic acid from SK&F 97426-A was also much slower (27 and 25%, respectively, dissociated after 60 min) than from cholestyramine (89 and 84%, respectively, dissociated after 60 min). The higher affinities and slower dissociation rates of the trihydroxy bile acids for and from SK&F 97426-A probably account for the increased potency of SK&F 97426-A over cholestyramine in vivo.

Drug interaction between simvastatin and cholestyramine in vitro and in vivo

The interaction between simvastatin (SV), a prodrug lactone, HMG-CoA reductase inhibitor which converts to the active hydroxy acid form (SVH) in vivo, and cholestyramine (CT), an anionic exchange resin, was evaluated both in vitro and in vivo. In an in vitro SV-stability study, it was shown that SV degraded gradually to SVH in an aqueous solution at pH 2 and 7. To evaluate the binding ability of SV or SVH to CT, the incubation of 5 micrograms/ml of SV or SVH solution with 200 mg of CT in various pH (2.0, 5.0 and 7.0) solutions was performed at 37 degrees C for 10 min. After incubation, the concentration of SV decreased by 59.02% (pH 2), 63.90% (pH 5) and 67.36% (pH 7), respectively, and an interaction between SV and CT was suggested. The values were much larger than those expected from the stability test of SV in the absence of CT. SVH was found to bind more strongly to CT. The binding ability of SVH to CT was 66.71% (pH 2), 87.44% (pH 5) and 92.11% (pH 7), respectively. Judging from these results, SV was considered to interact with CT by the following procedure: SV underwent hydrolysis to SVH in aqueous solution, then CT activated the hydrolysis by binding the formed SVH, resulting in a significant reduction in concentration of SV. On the other hand, an in vivo animal experiment also demonstrated a significant reduction (about 50% with AUC) in the concentration of SVH in plasma following the coadministration of SV (500 mg/kg p.o.) and CT (600 mg/kg p.o.), compared with the administration of SV alone. This phenomenon suggested that a combination therapy using SV and CT might result in a smaller cholesterol-lowering effect of SV.

Disposition of lorazepam in diabetes: differences between patients treated with beef/pork and human insulins

The pharmacokinetics of lorazepam was examined in 10 male patients with insulin-dependent diabetes mellitus before and following treatment with neomycin and cholestyramine. Neomycin and cholestyramine were given in an attempt to block the enterohepatic circulation of lorazepam and so to permit an in vivo estimate of hepatic glucuronidation. The volume of distribution and clearance of free lorazepam in diabetic patients were not significantly different from the corresponding estimates in 14 normal controls. Neomycin and cholestyramine increased the clearance of lorazepam by 63% consistent with their effect in non-diabetic controls. However, patients on beef/pork insulin exhibited a greater than normal increase on this interupting regimen (125%), and had a significantly greater neomycin/cholestyramine cycling-interrupted clearance of lorazepam than either normal controls or patients on human insulin (15.4 vs. 6.96 and 7.87 ml.min-1.kg-1). The clearance was correlated positively and significantly with HbA1c and glycated proteins (fructosamine), but only in patients on human insulin. Thus, the pharmacokinetics of lorazepam was not altered in patients with insulin-dependent diabetes mellitus. However, it is possible that there are differences in the rate and extent of hepatic glucuronidation and enterohepatic circulation of lorazepam between patients treated with beef/pork and human insulins and between diabetics treated with beef/pork insulin and non-diabetic controls.

The efficacy and relative bioavailability of diclofenac resinate in rheumatoid arthritis patients

The pharmacodynamics and pharmacokinetics of 75 mg resin-bound diclofenac (resinate) were compared with enteric-coated tablets containing 75 mg of diclofenac in a double-blind randomized crossover trial in 16 patients suffering from rheumatoid arthritis. Diclofenac was significantly faster absorbed from the resinate than from the enteric coated formulation (tlag = 0.454 h vs. 0.998 h, tmax = 1.41 h vs. 2.56 h) and reached lower peak concentrations (Cmax = 1.64 micrograms/ml vs. 2.59 micrograms/ml). No significant differences were found concerning the area under the plasma level-time curves and the mean residence times. Smaller variances were found for the tmax and the mean residence times in the group treated with diclofenac resinate. Onset and duration of analgesia, as assessed by visual analogue scales were similar in both treatment groups, but did not correlate with the plasma concentrations. Four patients experienced adverse effects including gastric pain, transaminase increases, proteinuria and plasma creatinin increase. No uncommon adverse effects were observed with the new preparation.

Pharmacokinetics of fluvastatin and specific drug interactions

Fluvastatin sodium (Lescol) is the first synthetic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA)-reductase inhibitor to be studied extensively in humans. Absorption of fluvastatin is complete and unaffected by the presence of food. Systemic exposure is limited because of extensive sequestration by the liver and/or first-pass metabolism, a plasma half-life of approximately 30 min, no circulating active metabolites, and no accumulation of drug during chronic dosing. Approximately 95% of a single dose of fluvastatin is excreted via the biliary route with less than 2% as the parent compound. Studies investigating the effect of food on fluvastatin pharmacokinetics have demonstrated marked reductions in the rate of bioavailability (Cmax) of 40% to 60%. A comparison of drug administration with the evening meal or at bedtime revealed no significant differences in either the extent of bioavailability (area under the curve; AUC) or pharmacodynamic effect [reduction in low-density lipoprotein cholesterol (LDL-C)]. Relative to the general population, plasma fluvastatin concentrations do not vary as a function of either age or gender. Administration of a single 40-mg dose to a patient population with hepatic insufficiency resulted in a 2.5-fold increase in both AUC and Cmax. Drug interaction studies with fluvastatin and cholestyramine (CME) demonstrated a lower rate and extent of fluvastatin bioavailability; no impact on efficacy was demonstrated when CME was given 4 h before fluvastatin dosing in clinical trials. Interaction studies with niacin and propranolol demonstrated no effects on fluvastatin plasma levels, and fluvastatin administered to a patient population chronically receiving digoxin had no effect on the AUC of digoxin compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of tricyclic antidepressants with cholestyramine in vitro

The adsorption of amitriptyline, desipramine, doxepin, imipramine, and nortriptyline onto cholestyramine was demonstrated in vitro with use of 1.2 mol/L HCl at 37 degrees C to simulate gastric fluid. Binding to cholestyramine was approximately 80% for each of the tricyclic antidepressants, and this was about the same degree of binding noted with a nonpharmaceutical, non-ionic resin widely used in the diagnostic toxicology laboratory (Amberlite XAD-2). In contrast, five other non-antidepressants (acetaminophen, chlordiazepoxide, procainamide, quinidine, and theophylline) showed only minimal binding to cholestyramine under these conditions. Activated charcoal completely bound all drugs studied. These findings suggest that cholestyramine should be used with caution in patients receiving tricyclic antidepressants. They also suggest that cholestyramine may be a potentially useful adjunctive therapy in treatment of overdose with the tricyclic antidepressants.

Pharmacokinetics and pharmacodynamics of pravastatin alone and with cholestyramine in hypercholesterolemia

The pharmacokinetics, pharmacodynamics, and safety of pravastatin, a new selective 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, were evaluated during monotherapy and with subsequent concomitant cholestyramine therapy in 33 patients with primary hypercholesterolemia in this randomized study. After 4 weeks, pravastatin monotherapy (5 mg, 10 mg, and 20 mg twice daily) significantly decreased total cholesterol by 17% to 24% (p less than 0.001 versus baseline) and low-density lipoprotein cholesterol by 23% to 35% (p less than 0.001). High-density lipoprotein cholesterol increased by 8% to 9%, and triglycerides decreased by 6% to 9%. The area under the serum concentration-time curve and maximum serum concentration of pravastatin showed dose-proportionality; time to maximum serum concentration and serum elimination half-life were independent of dose. When added to pravastatin therapy, cholestyramine enhanced the lipid-lowering effects of pravastatin. After 4 weeks of combination therapy, total cholesterol was reduced by 32% to 38% (p less than 0.001 versus baseline), and low-density lipoprotein cholesterol was reduced by 47% to 56% (p less than 0.001). High-density lipoprotein cholesterol increased by 11% to 18% (p less than 0.05). Pravastatin was well tolerated; no clinical adverse events directly attributable to the drug were reported.

[Interaction of cholestyramine and chloroquine]

The plasma levels of chloroquine after an oral intake of 10 mg/kg were measured in 5 children, with or without simultaneous intake of cholestyramine. Plasma chloroquine levels measured 6 hours after intake were significantly lower in case of simultaneous administration of cholestyramine, in spite of important individual changes. These data suggest a decrease in chloroquine bioavailability in the presence of cholestyramine. However, the methodology used does not allow to assert it.

Bile acid sequestrants

The bile acid sequestrants, cholestyramine and colestipol, are the drugs of choice for the treatment of patients with hypercholesterolemia caused by increases in LDL-cholesterol levels without concurrent hypertriglyceridemia (type IIA and type IIB hyperlipoproteinemia). Longitudinal clinical studies with these drugs have shown their ability to slow the progression of atherosclerosis and to limit the consequences of the disease. Bile acid sequestrants can be used with other lipid-lowering drugs such as nicotinic acid or HMG CoA reductase inhibitors, to maximize the cholesterol-lowering effects. The side effect profile of the bile acid sequestrants is tolerable, with most complaints related to effects on the gastrointestinal tract and the bulkiness of the resins.

[Influence of pH in the adsorption capacity of bile salts and lysolecithins in vitro by antacids containing clay and/or aluminum]

In vitro binding properties of eight clay and/or aluminium-containing antacids for bile salts and lysolecithin were measured in comparison with cholestyramine binding capacity, taking into account the final medium pH. Dihydroxy-bile salt adsorption was greater when the initial pH was 1.8 and the intensity varied according to the drugs. Trihydroxybile salts were less bound and the binding was less related to the medium pH. Lysolecithins were bound by clay-containing antacids with the same intensity as cholestyramine, while the binding capacity of aluminium-containing antacids was weaker and related to the final pH. There were close relationships between binding capacities and the final pH so that bile salts are bound by antacids with a great intensity in acid medium and released by alkalinisation in contrary to the binding capacity of cholestyramine. Lysolecithins should be also bound more intensively in acid medium by aluminium-containing antacids. Binding capacities of the antacids were related to their composition, their antacid effect and to the final pH.